The invention relates to a tool with self-locking grip, interchangeable head-pieces and clamp for fastening to a work bench.
It is well known that there is currently a vast range of work tools made up essentially of two levers, also known as gripping arms, which are permanently fastened to the handle, with at least one of the gripping arms or levers being mobile.
Jaws are generally provided at the end of the arms, for holding a workpiece. In some cases the ends of the arms comprise devices specially adapted to some operations, for example, for cutting a pipe, punching holes, etc.
These work tools are generally designed to perform just one task, depending on the type and shape of the jaws, the means provided for regulating the distance between the ends of the arms, and the possibility of locking the arms using a specific self-locking system.
For this reason, there is an almost endless variety of two-gripping arms tools on the market today, the more common of which being: self-locking pliers with screw-adjustment of the distance between the jaws and the locking pressure; adjustable pipe wrenches which allow the distance between the jaws to be set; wrenches featuring one movable jaw which slides along a worm screw-lead screw system; pipe cutters with cutting wheel set at the end of at least one of the gripping arms; punches for punching holes in soft sheet material, etc.
As a result, different operations normally require the purchase of different tools with greater expense and transport and handling problems.
U.S. Pat. No. 2,312,425 describes a wrench wherein it is easy to place the jaws in gripping relation to the work, and having interchangeable jaws of different contours, suitable to particular types of work.
The wrench comprises an elongated flat transversely rectangular casing having an open end and a closed end, and an elongated longitudinal slot in one edge thereof, a pair of jaw members having flat shanks extending into said open end of the casing and relatively slidable in edge-to-edge engaging relation therein, inwardly and outwardly of said open end, respectively, into different positions, detent means for releasably holding one shank in different positions, a spring in said casing having its ends fastened to the inner end of the other shank and to the closed end of the casing, respectively, in the line of movement of said other shank and tensioning said other shank against outward sliding, and means to slide said other shank outwardly in opposition to said spring comprising a lateral edge lug on said other shank extending into the slot in said one edge of the casing flush with said edge, a pair of opposed ears extending from said one edge of the casing at opposite sides of said slot, a cam pivoted between said lugs and having a handle and a radial shoulder rotatable into said slot into camming engagement with said lug.
The main disadvantages of the wrench consist in that is difficult to unfasten the spring and to interchange the shank without disassembling the casing.
The interchangeability is theoretic more than practical.
Moreover, the thickness of the object to be gripped does not allow the handle to find a rest in the casing.
Furthermore, the user must hold the wrench in his hand while he is working, and this means that one hand is constantly engaged.
Finally, the compression of the handle always causes the lower jaw to move towards the upper jaw, whereas in some works it is more convenient that the upper jaw moves towards the lower one.
In U.S. Pat. No. 2,149,541 a wrench is disclosed having a handle and a pair of complemental jaws. The jaws have some type of removable jaw members attached to the regular jaws of the wrench, in order to provide alternatively a smooth flat clamping surface on the jaws, or a punch member, or a cutting pipe device.
The main defect consists in that the jaws are not interchangeable, but may just be fitted by applying thereto devices of reduced dimensions, which aren""t practical and are weak. Further disadvantages consist in that the wrench lacks a device for blocking the jaws in position, and that the push of the user on the handle is not balanced, thus forcing the user himself to use not only one, but both hands to do his work.
Furthermore, none of the more commonly available tools has the option of being fastened directly to the work bench; indeed, even tools designed to hold two objects for operations such as welding or gluing, must be fastened to the bench using a traditional vice, in order to allow the user to have both hands free.
Said bench vice, may also damage or deform the handle of the tool.
The aim of this invention is to eliminate all of the problems described above.
In particular, the main objective of the invention is to realize a tool with removable and interchangeable gripping arms, for performing a wide variety of tasks.
A further objective is the possibility of fastening the tool to the work bench using a specific, incorporated device, which is operated by the same self-locking system of the arms.
These and other objectives are fulfilled by the invention, a self-locking tool comprising a handle, two gripping arms and a self-locking system, wherein the handle of the tool comprise a main body with two prismatic housing-guides, holding and guiding said two arms; the arms are removable and interchangeable with other arms and fitted with ends adapted for performing a range of mechanical functions; the self-locking device is connected between the body of the handle and one of the arms, so that operation of the device causes a sliding of said one of the arms, whose end approaches the end of the other gripping arm, this last being fixed inside its housing, to give a gripping effect and locking into position when closed.
The main body of the handle contains at least a third prismatic housing-guide, for a further removable gripping arm at the opposite end of the handle; this arm being connected to the same self-locking device and sliding inside its housing, for fastening the tool to a workbench, in cooperation with a fixed element.
Moreover, the gripping area of the ends of the arms is advantageously fitted with removable devices which can be easily replaced.
The advantages of this invention consist, in general, in the fact that several different applications can be performed using one single handle, costs for the purchasing of a complete kit of tools are reduced, and the user can work alone, without using a vice to clamp the wrench.
Further advantages are the possibility to obtain a greater opening of the jaws at the end of the gripping arms; the possibility to have a progressive pressure between the end of the gripping arms using a claw device, fitted in the self-blocking lever (useful, for example, when cutting pipes); the high force allowed by the kinematic movement of the self-locking lever (useful for example, to trim or punch), etc.